The present invention relates generally to biocides for water systems such as swimming pools, spas, cooling towers, or other industrial applications, and more particularly to biocides using copper, silver or zinc as their active agent.
Certain metals, such as copper, silver, zinc, etc., are known to possess biocidal qualities when used in circulating water systems. Unfortunately, many metal ions easily precipitate in alkaline or near-alkaline water conditions as insoluble salts of oxides, hydroxides, and/or carbonates, removing the metals from the system and thus removing the ability of the metal ion to act as a biocide.
In order to improve the efficacy of metals to act as biocides in water, sequestering agents, such as alkanolamines, aminocarboxylic acids or citric acid have been used to improve the stability of the metal in aqueous solutions conditions. These simple, organic compounds contain amine, hydroxyl, and carboxyl functionalities that exhibit sequestration capacity for polyvalent metal cations. Problems remain however, because alkanolamines, aminocarboxylic acids, and citric acid deteriorate quickly in the presence of halogens and other oxidizers, bacteria, sunlight or heat, thus allowing the metal to become unsequestered and subject to loss due to precipitation. The net result in pools, spas, cooling towers or other water systems is a loss of activity of the metal ions.
Another problem encountered in water treatment applications, such as swimming pools or spas, is that metals precipitate to form unsightly stains on the pool""s surface. In particular, metal hydroxides, metal oxides and metal carbonates are known to cause unsightly stains that are difficult to remove.
A need therefore exists for a method of stabilizing soluble metals for longer periods of time during treatment and application, thereby increasing their effective life and preventing stains from occurring on swimming pool surfaces. The present invention addresses that need.
Briefly describing one aspect of the present invention there are provided metal-containing biocides for treating swimming pool water without staining the sides of the pool. The inventive biocidal compositions include a source of a metal such as copper, silver, zinc, etc., and a polymeric sequestering agent. The polymeric sequestering agent may be a water-soluble anionic polymer or a water-soluble cationic polymer. Conventional sequestering agents may also be included in the composition.
One object of the present invention is to provide metal-containing biocides that do not stain the solid surfaces of a swimming pool.
A second object of the present invention is to provide a metal-containing biocidal composition that maintains activity longer due to stabilization of metal ions in solution by polymeric sequesterants.
Further objects and advantages of the present invention will be apparent from the following description.